Related Rule
Practice Relating to Rule 12. Definition of Indiscriminate Attacks
Section B. Attacks which cannot be directed at a specific military objective
In 2008, in a joint cost benefit analysis of a possible introduction of a national moratorium on all cluster munitions, Denmark’s Ministry of Defence and Ministry of Foreign Affairs stated:
[The] provisions, which are outlined below, are generally recognized as being an expression of customary international law. …
The purpose of international humanitarian law is to protect the victims of war as much as possible. …
It follows from API [1977 Additional Protocol I] that military attacks that do not respect the distinction between civilians and military targets are illegal because of their indiscriminate nature. Such indiscriminate attacks are defined in API Article 51(4). 
Denmark, Ministry of Defence and Ministry of Foreign Affairs, A Cost Benefit Analysis of a Possible Introduction of a National Danish Moratorium on All Cluster Munitions, 1 April 2008, p. 15.